Earlier quoted context omitted.
This is an interesting question for two-sided operations like Google and Facebook. Having a near-monopoly in online search also gives Google a near-monopsony in online search advertising. Likewise for Facebook with social networking. I'm wary of introducing regulation without clear evidence of its necessity. However, there is a reasonable argument that if exploiting a monopoly to gain advantage in an adjacent market…
I'm sorry, but what are you suggesting is harmful here?
Prices paid by the advertisers more generally, for another. There are only two games in town, and both of them go out of their way to obscure what you're really getting in return for your money.